Power supplies are typically discrete assemblies that are mounted to a device chassis, or are mounted separately from assemblies that facilitate data processing. However, to conserve space and provide other benefits, many designers are attempting to integrate power supplies or voltage regulators onto motherboards proximate to processors, memory and various other data processing circuits. Such integration presents many design challenges. For example, precision control signals are required to operate switching power supplies and generating such signals on a motherboard in not a trivial design task. Further, for such integration to be feasible, a low cost approach for generating power conversion control signals on a motherboard becomes a concern. One way to achieve a low cost solution is to utilize existing hardware such as a processor to create or generate the control signals. However, processor based control signals on a motherboard typically utilize relatively low voltages. For example, processors are often powered by five volts and the digital logic on the output of a processor is often near one volt. Power conversion control systems typically require control signals for power transistors that are in the five volt range, thus a processor output cannot be utilized to control a power supply without some signal conversions. Further, processors typically cannot supply enough current to control or switch the power transistors of the power supply or power converter.
Allowing a processor, existing “onboard” logic, or a data processing circuit to control power transistors can eliminate the need for a large bulky and expensive external power supplies. Another positive feature of onboard power supplies is that, since the supply voltage is regulated near the load, voltage drops and interference caused by relatively long transmission lines can be minimized. Further, redundancy can be achieved due smaller and more numerous power supplies or voltage regulators (VR)s that are supplied with control signals locally, by a processor.
A power converter or VR will typically have power transistors that switch “on and off” to pass a portion of the power or voltage at the input of the VR to the output of the VR. The amount of voltage drop provided by the VR depends on the average “on” time of the power transistors in the VR. Many modern power converters topologies utilize a multi-phase configuration that requires multiple drive signals and there is often a lack of available pins on a typical processor to provide such multiple outputs. Thus minimizing the amount of pins required to control multiple power transistors is another design consideration.